Fuel injectors for controllably metering fuel to the combustion cylinders of internal combustion engines are well known. Modern engines typically incorporate a dedicated fuel injector for each cylinder, the fuel injector being disposed in the intake port or runner from the intake manifold to the cylinder. For ease and reliability in manufacturing, the fuel injectors typically are mounted by their inlet ends at appropriate intervals into a rigid fuel supply line harness, appropriately configured to place the injection end of each fuel injector into its corresponding injection socket in the manifold runner. Such a harness is known as a fuel injector rail, or simply a fuel rail.
In a typical direct injector fuel injection system, each injector is programmed to pulse or open every other revolution of the engine crankshaft. During an injector opening event in a direct injector fuel injection system, the measured fuel pressure in the fuel rail can instantaneously drop by more than 30 kPa, then can increase by more than 50 kPa after the injector closes. For a typical four cylinder engine operating at 2000 RPM, the combined injectors pulse at a rate of 66 pulses per second. In such injector-based systems, these pulses, dropping then raising the pressure in the rail, cause high frequency pressure waves of significant amplitude to propagate through the fuel rail(s) potentially causing erratic delivery of fuel to the cylinders. This condition is aggravated even further in an Air Pressure Direct Injector (APDI) system where a pair of injectors (which separate the fuel metering event from the fuel delivery event) firing out of phase, each at 66 pulses per second, induce pressure pulsations into the fuel rails.
The fuel rails themselves are typically bolted to the cylinder head. In one prior art method seen in FIG. 1, the fuel rail 10 is laterally offset from the position of the bolts (not shown) which are secured to the cylinder head (also not shown) through brackets 12. The fuel rail 10 is offset so the bolts are accessible when attaching or removing the fuel rail from the cylinder head. In this embodiment, the brackets 12 extend around a respective fuel injector socket 14, into which the inlet ends of the injectors (not shown) are placed. This prior art design requires a jumper tube 16 leading from the rail 10 to the respective socket 14. It also requires additional brackets 18 positioned on the side of the rail opposite the socket side to firmly secure the rail in place on the cylinder head. This prior art method has several serious drawbacks. First, the brackets require very tight tolerances due to the high pressure forces generated by the fuel injectors. Due to the excessive amount of bracketing required in this design, the tolerance stack-up is high and difficult to effectively and consistently control. The prior art design also requires a jumper tube 16 due to the lateral offset of the rail with respect to the injectors. The jumper tubes not only impart additional part cost, but also introduce additional tolerance locations that need to be controlled as well as seals that may leak. It would therefore be desirable to have a method and design for securing a fuel rail to a cylinder head that reduces or eliminates the amount of bracketing required. It would furthermore be desirable to have a method and design for securing a fuel rail to a cylinder head that does not require jumper tubes.